咸水滴灌条件下塔里木沙漠公路防护林土壤水分物理性质

The Soil Water Physical Properties in the Tarim Desert Highway Shelterbelt Under Saline Water Drip-irrigation

应用压力膜仪测定了塔里木沙漠公路防护林地0-150cm土层范围内的土壤水分特征曲线,并用RETC软件中的van Genuchten模型对其进行拟合分析,研究了防护林地不同土层的土壤水分物理特性。结果表明:(1)van Genuchten模型拟合的含水量模拟值与实测值间的RMSE≤0.01。(2)各土层持水性强弱依次为0-5cm>40-60cm>100-150cm>60-100cm>5-40cm;供水性表现为5-40cm>60-100cm>0-5cm>40-60cm>100-150cm,且整体在低于1.5×105 Pa吸力值时表现较强;各土层有效水含量自上而下递减,均值为17.286%。(3)饱和持水量、毛管持水量和田间持水量也随土层自上而下呈同步下降趋势,并与容重呈显著的一元线性负相关。(4)有效水范围内,防护林地土壤有效水上限对应0.3×105 Pa的吸力值,易效水与难效水的临界点吸力值以1.5×105 Pa为宜;各土层的易效水均多于难效水,总体上,前者均值为13.127%,是后者的3倍;5-40cm和60-100cm土层的易效水多,0-5cm和40-60cm土层的难效水多,二者比例均为同类最高;同层内易效水比例与土壤持水性之间负对应。

The soil water characteristic curves for different depths from 0cm to 150 cm of the soil profiles in Tarim desert highway shelterbelt were measured by Pressure Membrane Apparatus and fitted by van Genuchten,then the soil physical water properties for different depths were analyzed and revealed.The results showed as follows：（1）It was significant to imitate the soil water characteristic curves for different depths in this study area with the help of van Genuchten Model,because all the results of RMSE between simulated values and measured values of soil water content had reached remarkable levels which were not more than 0.01.（2）From strong to weak,the capacity of soil water retention for different depths were followed respectively by 0-5cm,40-60 cm,100-150 cm,60-100 cm,5-40 cm while the soil water supply were followed respectively by 5-40 cm,60-100 cm,0-5cm,40-60 cm,100-150 cm,and it took on a strong water supply under the soil suction on Pressure which was less than 1.5×10^5 Pa.The available moisture content of soil was decreased gradually from the upper depth to the lower depth and its average was17.286%.（3）Saturated moisture capacity,capillary moisture capacity and field moisture capacity were also showed a synchronized decreasing trend from the upper depth to the lower depth;on the other hand,the relationship was closed between three kinds of soil moisture holding-capacity and soil bulk,which was consistent with one-linear regression function.（4）The upper limit of available water was the soil moisture content corresponding to the suction of 0.3×10^5 Pa and it was suitable to take 1.5×10^5 Pa as the boundary point ofsuction for readily available water and resistant available water.The readily available water content in all the depths were more than the resistant available water content,and the value of former was 13.127%,which was three times of the latter.Compared with the others,the readily available water content in the depths of5-40 cm and 60-100 cm took the most supreme proportion while the resistant available water content in the depths of 5-40 cm and 60-100 cm took the highest proportion in the range of available soil water content,and both the values of them were the biggest.Besides,the bigger the proportion of readily available water content,the weaker the capacity of soil water retention in the same depth.